Process for the production of cellulosic sheets



April 7, 1959 A. LUCHTENBERG PROCESS FOR THE PRODUCTION OF CELLULOSIC SHEETS Filed Jan. 11, 1956 FIG. 1

3 mm F INVENTOR: ALEX LUCH TENBERG ATT'YS PROESS FBR THE PRODUCTION 9F CELLULGSHQ SHEETS Alex Luchtenberg, Milspe, $ransel, (Germany, assiguor to J. P. Bemberg Alrtiengesellschaft, Wuppertaidlherhanmen, Germany Application January 11, 1956, Serial No. 558,593

Claims priority, application Germany January 15, 1955 1 Claim. (U. lit-=57) This invention relates to process for the production of cellulosic sheets from cellulosic solutions.

In the so-called apron pouring process for the production of cellulosic sheets from cellulosic solutions, the solution is extruded downwardly through an elongated slot into a coagulation bath. Since the temperature of the coagulation fluid in the bath is the same or higher than that of the solution in the pouring device positioned in a certain distance above the surface of the bath, vapors from the bath fluid condense around the pouring slot. Drops of liquid formed by the condensation then fall on the extruded film causing holes or streaks.

In order to prevent the aforementioned condensation, it has been proposed that the pouring solution or the metal block which forms the pouring apparatus be preheated to a temperature a few degrees higher than that of the coagulation bath. However, this method has not been entirely satisfactory since it requires a very considerable quantity of heat.

It is an object of this invention to provide a process for the production of cellulosic sheets which avoids the condensation of bath vapors around the pouring slot.

It is a further object of the invention to provide a process for the production of cellulosic sheets in which the condensation of bath vapors around the pouring slot is avoided by a minimum heating of the pouring device.

Other objects and advantages of the invention will become apparent during the course of the following description.

In the accompanying drawings forming a part of this application and in which like numerals are employed to designate like parts throughout the same,

Fig. 1 is a front vertical section of apparatus employed by the process invention including a pouring device, heating elements, and a coagulation bath;

Fig. 2 is a fragmentary side elevation of a heating element and the pouring device shown in Fig. 1; and

Fig. 3 is an enlarged cross section of the heating element shown in Fig. 2.

In accordance with the process invention the objects are accomplished by an apparatus comprising a coagulation bath in combination with a pouring device having externally heated pouring lips.

In the drawings wherein for the purpose of illustration is shown a preferred embodiment of the invention, Fig. 1 shows a pouring device or receptacle 1 containing a cellulosic solution 2 such as viscose rayon. The bottom of the pouring device has a pair of elongated pouring lips 3 and 4 having an elongated pouring slot 5 therebetween. A pair of electric heating elements 6 and 7 are positioned in contact and coextensive with the exposed surfaces of the lips 3 and 4 respectively. Each of the heating elements 6 and '7 contains a resistance Wire 8 such as chromium-nickel Wire. The wire 8 is surrounded by a granular insulating material 9 which may be a form of talc such as steatite beads. The Wire 8 and the insulating material 9 are encased in a tube 10 of a metal such as iron.

The pouring device 1 is positioned above a coagulation bath comprising a tank 14 containing a coagulation fluid 11. During use of the apparatus the cellulosic solution 2 in the pouring device 1 emerges from the slot 5 as a cellulosic film 12 and falls freely into the coagulation fluid 11. Electricity in amounts controlled by a voltage regulator 13 is passed through the heating elements 6 and 7 so as to heat the pouring lips 3 and 4. The voltage is controlled by the regulator 13 so as to heat the lips 3 and 4 to a temperature a few degrees higher than that of the coagulation fluid 11.

By means of the invention, employing electric heating elements along the length of the pouring lips, the heating of the pouring device is limited or localized to the surface Where drops would otherwise form. The heat energy required by this means is considerably lower than that required by any previously devised means for preventing the condensation.

The invention is hereby claimed as follows:

A process for the production of a cellulosic sheet which comprises extruding a cellulosic solution in the form of a film from an elongated slot of a pouring device through an air space into an open, aqueous coagulation bath positioned below the pouring device and heated to a temperature at least equal to the temperature of the cellulosic solution being extruded, and preventing the condensation of vapors rising from the coagulation bath on surfaces of the pouring device adjacent said slot by the application from an electric heating source external of and in heat conducting contact with said pouring device of only sufficient, localized, electrical energy heat along the entire exposed surfaces of the pouring device adjacent said slot to give the exposed surfaces adjacent said slot a temperature slightly greater than the temperature of the bath, whereby the formation of condensate drops on said exposed surfaces from vapors arising from the bath and subsequent contact thereof with the cellulosic film being extruded is avoided.

References Cited in the file of this patent UNITED STATES PATENTS 2,045,348 Dreyfus June 23, 1936 2,177,660 Kimble et al Oct. 31, 1939 2,325,574 Wunderer July 27, 1943 2,468,585 Bluma Apr. 26, 1949 2,564,836 Elsenheimer Aug. 21, 1951 2,617,325 Astle Nov. 11, 1952 2,672,729 Van Ry Mar. 23, 1954 

